1. Technical Field
This invention relates generally to techniques for acoustic calibration of one or more audio output devices (e.g., loudspeakers), and more particularly to techniques which utilize multiple wireless audio input devices (e.g., wireless microphones) for performing such calibration.
2. Background Art
Home theaters typically include a receiver (and/or preamplifier and/or amplifier) coupled to a plurality of speakers which collectively function to provide an immersive audio experience within a listening area. However, home theater setup requires proper calibration of speaker levels, speaker distances and equalization to get the full immersive experience intended by content creators. Calibration typically includes setting speaker and subwoofer volume levels and the speaker-subwoofer crossover point, as well as employing equalization to balance the frequency response of all the speakers and try to minimize room acoustic problems.
Many commercially-available home theater output devices include an automatic speaker calibration system which sends test tones through all of the speakers and the subwoofer and uses a single wired microphone to capture the sounds of the speakers at one or more locations.
Many conventional arrangements involve taking measurements at a single location within the listening area (e.g., one seat in a room), and thus only attempt to optimize the listening experience for that single location. For example, the EzSet® system was developed by Harman International Inc. utilizing technology described in U.S. Pat. No. 5,386,478, the disclosure of which is incorporated herein. Literature available on Harman International Inc.'s website on the filing date of the present application is submitted herewith and incorporated by reference herein. Other techniques involve the use of multiple microphones at a single listening location, such as the techniques disclosed by U.S. Pat. No. 6,954,538 and U.S. Pat. No. 7,095,455, the disclosures of which are incorporated herein.
However, the aforementioned techniques each only attempt to optimize the listening experience for a single listening location within a listening area. Each of the aforementioned techniques therefore suffer from a significant disadvantage in that optimizing the listening experience for a single location typically results in a diminished listening experience at other locations within the listening area (e.g., other seats in the room) because a measurement at a single location cannot provide an accurate representation of the acoustical problems present within the entire listening area. Other techniques have been developed which attempt to address this problem by utilizing measurements obtained at multiple locations to attempt to optimize performance for multiple listeners within a large listening area.
The ADAPTiQ® audio calibration process was developed by Bose® utilizing technology described in U.S. Pat. No. 7,483,540, the disclosure of which is incorporated by reference herein. Literature available on Bose's website on the filing date of the present application is submitted herewith and incorporated by reference herein. The MultEQ® acoustical correction technology was developed by Audyssey Laboratories utilizing technology described in U.S. Pat. No. 7,567,675, the disclosure of which is incorporated by reference herein. Literature available on Audyssey Laboratories' website on the filing date of the present application is submitted herewith and incorporated by reference herein. The RoomPerfect® audio calibration process was developed by Lyngdorf utilizing technology described in U.S. Pat. No. 8,094,826, the disclosure of which is incorporated by reference herein. Literature available on Lyngdorf's website on the filing date of the present application is submitted herewith and incorporated by reference herein.
The ADAPTiQ®, MultEQ®, and RoomPerfect® processes each involve the use of a single wired microphone to make a series of measurements sequentially as the single wired microphone is moved to multiple locations within the listening area. Measurements typically need to be taken at between 3 and 32 locations, which can be a very time-consuming and tedious process.
Room EQ calibration was developed by Harman International Inc. utilizing technology described in U.S. Patent Application Publication No. 2006/0147057, the disclosure of which is incorporated by reference herein, and is commercially available in Harman International Inc.'s Lexicon® MC-12 and MC-12 Controllers. Literature available on Harman International Inc.'s website on the filing date of the present application is submitted herewith and incorporated by reference herein.
Room EQ calibration uses four wired microphones to simultaneously measure acoustical characteristics at multiple locations within a listening room. The multiple wired microphones are all connected to a single signal block which stores raw samples from the multiple microphones and the single signal block calculates the frequency response of each microphone.
Although Room EQ calibration offers certain advantages relative to the ADAPTiQ®, MultEQ®, and RoomPerfect® processes by allowing for simultaneous, rather than sequential, measurement of acoustical characteristics at multiple locations within a listening room, each of these processes requires the use of a specific wired microphone. Each of these processes explicitly warns that use of any other type of microphone (e.g., a wireless microphone) would result in inaccurate results. Moreover, modifying these arrangements to utilize one or more wireless microphones would require substantial redesign of the receivers.
However, the use of a wired microphone has disadvantages: moving between locations with a wired microphone can be cumbersome, especially where these locations are distant from the receiver or from each other. For example, distributed audio systems are installations where there are many rooms with speakers that have speaker cables that run back to a central equipment location, such an equipment closet, where the receiver (and/or preamplifier and/or amplifier) may be located. Distributed audio systems are often difficult to calibrate due to the distance between the centralized equipment location and the room where the speakers are located. These difficulties are exacerbated by the use of a wired microphone for calibration, which may require the microphone cable to go up or down stairs and/or travel down hallways to reach the room in which the speakers to be calibrated are located.
Other conventional arrangements include Pioneer Corp.'s MCACC® (Multi-Channel Acoustic Calibration), Sony Corp.'s DCAC® (Digital Cinema Auto Calibration), Yamaha Corp.'s YPAO® (Yamaha Parametric Room Acoustic Optimizer), Samsung's ASC (Automatic Sound Calibration), JBL's RMC (Room Mode Correction), and TaCT Audio's RCS (Room Correction System) originally developed by Snell Acoustics. Each of these conventional arrangements requires the use of a single wired microphone to make measurements at one or more locations, and thus suffers from one or more of the deficiencies discussed above.
Telex Communications Inc. has sold systems referred as the Electro-Voice® RTM-1 Remote Test Wireless System and the Electro-Voice® RTM-1000 Remote Test Wireless System, and Lectrosonics® sells a system referred to as the TM400 Test and Measurement Wireless System. Literature describing these systems is submitted herewith and incorporated by reference herein.
As described in the accompanying literature, each of these systems includes a single wireless transmitter which is paired with a single wireless receiver in that the transmitter and the receiver utilize the same wireless channel. The signals transmitted wirelessly from a given transmitter to a given receiver over a given wireless channel are raw audio signals, with optional companding (compressing/expanding) for greater dynamic range. The single wireless receiver is only able to receive and process signals from the single wireless transmitter, which in turn is connected to a single (wired) microphone via a cable. Simultaneous utilization of multiple microphones with these systems would require the use of multiple receivers paired with multiple transmitters, with each receiver-transmitter pair operating over a different wireless channel, and would also require substantial modifications and/or redesigns of the receiver(s) so as to allow for processing of signals received from multiple microphones rather than from a single microphone.
Thus, there is a long-felt need for an acoustic calibration system which permits the use of multiple wireless microphones, preferably utilizing a single receiver and a single wireless channel, to perform simultaneous measurements at multiple listening locations within a listening area.